ModifierRacing

What do you guys prefer? I have always used a th400 in my street/strip 10 second cars, and I have never built a GM full race car. For all the mustangs I have built I used either a c4 or c6. I am building a 86 camaro from scratch. I am planning on running mid 8s with a target weight of 3,000 lbs. I am going to run an alcohol injected big block. I was thinking the th400 would help with the launch since it is going to be heavy.

AlkyIROC

There's advantages to both. I know a local SuperGas racer who uses a TH400. I like the PG myself.

The TH400 has that extra gear so you can stay in a higher powerband. The PG's 2 gears means you do one shift around the 1/8 mile mark.

Using a TH400 gives a deeper first gear to get you off the line quicker. The PG's first gear is like launching in second gear. It might not be as quick but it's more consistant with a softer hit and you don't have to quickly shift gears as soon as you're out of the hole.

The TH400 eats up around 44 hp. The PG only uses about 18 hp.

The TH400 has a larger output shaft so you need to find the bigger slip yoke. The PG uses the same slip yoke as a TH350 or 700R4.

The TH400 is longer which will require a shorter driveshaft and a special tranny crossmember. The PG is a direct swap with a TH350 which can easily replace a 700R4.

Parts for a PG are cheap. Change the input shaft to a stronge aftermarket version with turbo splines. Change the factory cast direct hub with an aftermarket steel or aluminum hub. Change the servo piston with a dual ring piston and go racing with it.

To run mid 8's with a 3000 pound vehicle, your engine will need to make about 1100 HP. Mine only makes about 830

onefast85

he will need a good glide to run mid 8's unless he want to work on it all the time.

i would go glide for sure if you have over 100op as you will need to run mid 8's.

my car runs low 8's with a glide at 3400lbs.598 with a bunch of juice.

and with a glide you shift about the 330ft mark..not the 1/8.

IHI

iTrader: (1)

It'll be a hellava lot easier to hook up the hp your gonna need with a glide as opposed to a 3 speed. With the 400 you'd be pushing the limits of traction due to granney gearing unless you have a really loose convertor. Just had a buddy swap out his TH400 for a glide-nothing else changed even reused the same convertor in his BBC 68 camaro that weighs 3400lbs and ran 11.4x after the glide swap he lost .1 is all. Granted combo s are gonna work differently for guys, but dont let weight alone try to dictate which tranny to use.

I weighed my pig before it blew up and it came in at 3620lbs and I am seriously considering selling this TH400 and getting a glide built to soften the hit on my small tires.

And shift points will vary, only driven 3 glide equipped car down the track, but all of them were shifted within 20-30' of the 660'

I'm thinking if your having to shift by the 330' your convertor is waay to loose and your losing ET from slippage.

AlkyIROC

Sometimes you want to short shift. The sooner you get into high gear, the sooner then engine can pull with full hp.

I launch at 4500. My converter stalls at 5700. If I run the rpms up to 7000 in first gear, I'm usually at the 660 mark. If I short shift at around 6000, I'm before the 660 mark and can usually run a quicker ET. I'll cross the finish line at 7000 if I short shift or not.

Watch a SuperGas, SuperComp car go down the track. They'll use a throttle stop about 2 seconds out of the hole. When they come off the throttle stop, they're in high gear and don't do another shift all the way down the track.

Modifying the PG as a high gear only tranny by using a bunch of clutches in the high gear clutch pack means you have no shifts going down the track. You also need a light car or oodles of torque to get you off the line.

SnkSknrZ28

iTrader: (2)

i agree with IHI, with taht much power i'd say go glide.. How big f a tire will this car have? if its a backhalved car with big meats in the rear th400 would be cool, however if your usign a stock style suspension car with a 10.5 tire the th400 will be too much.. I have a 550hp SBC and i'm on the ragged edge of traction using a tranny brake, i have to launch using a 2step at 3000rpm as opposed to leavign off of my 4500stall convter and there are times when it still blows the tires away..

Motor City Mike

IMO, traction is the key to choosing which is best for your car. I have a back-halved car and I really like my TH400. I've gotten 1.29 60' times on very old, worn out 14x32 tires under crappy TNT track conditions. I can't possibly see a PG being quicker in my car.

onefast85

were any of the cars as fast as mine?i may be shifting at the 330 but look at the hp and et the car runs.lately i have been running 1/8 mile only.shift at 7200 and cross at 7200 in the 1/8..1.23 60ft..5.29 at 135mph.950hp 598 with 650hp worth of giggle gas on top and at 3400lbs.

IHI

iTrader: (1)

aaahh, car set up for the 1/8mi. explains everything

84406

I shift before the 330 with my glide and everyone that I know with a glide shift before the 330. If you did a quick calculator check, these 130 mph cars would be doing roughly 75 mph at the 1\8 if that is where they shifted.

ModifierRacing

The car will be on 10.5w tires, most likely 29.5x10.5w MT. I want to stay with that size tire for as long as I can, so I can run in alot of different classes.

Dan

onefast85

no not really.all the money racing in texas is 1/8 mile.i run it 1/4 but only one one kit.been 161 so far.

IHI

iTrader: (1)

With short shifting in the 1/8mi at the 330', what does that do with your 1/4mi trap rpm? if your crossing at 7K plus in the 1/8th how much more are you actually gaining by the 1320?

Just seems weird to think even with the 3 speed cars I've piloted I've gone through 2 gears before the 1/8th mi mark and your doing the gear change at 330' with a 2 speed, for 1/8mi racing I can understand that and would like to know how that equates into 1/4mi rpms, I race at an 1/8 mi track as well and some of those guys also come up here to our track 1/4mi and for the most part many said they did'nt cross a heck of lot higher that what they expected too-typically within 700-1200rpm of their 1/8mi rpm.

cp87GTA

You can also soften the hit on the tires by going with less stall! More stall is not always better. I started the season with a 4500 that flashed 5100 in my car. Blew the tires away alot, if the track wasn't perfect. Also blew 2 tranys and 2 rearends. After I broke the bell off of the 2nd trans, I desided to tame it back down. I don't get the foot and half air under the front tires anymore, but the car hooks and goes. Didn't loose any ET. Maybe gained a little and about 2 mph faster on top. Don't get that neck breaking leave anymore, but I can live without the headaches. Leaving at 3200 on a 3500 that flashes at 3700.

onefast85

i don't call 7200rpm short shifting.72 in the 1/8 and 7600 in the 1/4.on 1 kit i run 130 in the 1/8 and 161 in the 1/4.thats a 31mph increase which is very normal in a race car.

IHI

iTrader: (1)

Obviously it's working for you, but never heard of only picking up only 400 rpm in an 1/8 of a mile- the back half of the 1/8th and actually your only picking up 400 rpm in 990'??? since you shift at the 330' mark at 7200rpm? If that is really the case I still say excessive convertor slippage.

But hey, whtever works.

onefast85

read what you wrote again.

yep i shift at the 330 at 7200 but the rpms drop to 6800. so it gains 800rpm by the 1/4.the reason for that is it has a tight 10inch nitrous converter.


step up to some big boy hp and you will understand.just be ready for the cost.LOL

IHI

iTrader: (1)

LOL, building is actually the cheap part in the big picture, it's the entry fees, tires, gaz, and entry fees that getya....reason I'm taking a break next season, looking back at what I spent over these past 4 years....I could've paid for my house, all of our bills, cars, etc....luckily I do it cash so nothing hanging over my head, but once you get bit, hard to stop wanting more

Get some other things done around here to get the house completely done and shop built (1 year off from racing will easily do that) and then start planning next venture, aint no way I'll build a BBC unless it's ***** wild...too many unimpressive ones running around here.

onefast85

i bet my 598 would liven your car right up.LOL.

and its getting big duke heads this winter so it should make close to 1100hp on just motor.

Randy82WS7

uhm theres two lengths of the th400......

so which you guys talking about here ?

shorty or the long one ?

IHI please answer this ?

what length 400 did he have ?


thanks

IHI

iTrader: (1)

I got the short tail, dont know exact measurements so cant help ya there.